Voltage regulating apparatus



Patented Oct. 18, 1932 UNITED STATES PATENT OFFICE LEE DEVOL, OF FOREST HILLS, PENNSYLVANIA'ASSIGNOR TO THE UNION SWITCH 8a SIGNAL COMPANY, OF SWISSVALE, PENNSYLVANIA, A CORPORATION OF PENN- SYLVAN IA VOLTAGE REGULATING APPARATUS Application filed September 5, 1931. Serial No. 561,412.

My invention relates to voltage regulating apparatus, and particularly to apparatus wherein a resistance element having the prop-. ertyof "vary ng 1ts resistance in response to.

changes in the current density therein is used as the regulating :mediuin.

I will describe three forms of apparatus embodying my invention, and will then point out the novel features thereof in claims In the accompanying drawing,Fig.'1 is a diagrammatic view showing one arrangement of apparatus embodying my invention.

Figs.2.and '3 show modified arrangements of the apparatus of Fig. 1, also embodying my invention.

Similar reference characters'refer to simisulting from variations in the supply voltage v is illustrated in -Fig. l, which shows two oppositely poled asymmetric units R and R connected inseries With a resistor F, across an alternating current AB. The asymmetric units R and R are of such character that variations in the current density therein produce variations in the resistance of the respective units. One type of asymmetric unit having the desired characteristics and which is particularly well suited for use in my invention is the copper oxide rectifier described and claimed in United States Letters Patent No. 1,640,335, granted to L. O. Grondahl on August 23, 1927 It is a well-known characteristic of the copper oxide rectifier that for a considerable range of current density, the resistance in the low resistance direction through the rectifier decreases with an increase in the current density. Also, for a range involving current densities which are not too great, the resistance of the rectifier in the high resistance direction increases as the current density in creases. In the arrangement shown in Fig. 1, advantage is taken of the latter property of the copper oxide rectifier to decrease valows that, disregarding resistor F for the moment, theresistance ofi'ered to current 1 passing through the rectifiers R and R is predominantly the resistance of the rectifier which is poled opposite to the direction of current flow.

Assuming that the instantaneous polarity of the current is such that current flows into the circuit at point A of the source, the drop across rectifier R will be much greater than the drop across rectifier R and if the con- -ducting area of rectifier R is suitably chosen with regard to the current flowing therethrough aspartly determined by the resistance of resistor F and the impedance of load L, the current density for current in the high resistance direction through rectifier R will be within the range in which an increase in the density produces an increase in resistance. It now the voltage at the source 'AB increases, the current through rectifier R will increase, and will produce an increase in the resistance of rectifier R The resistance of rectifier R in the low resistance direction will, in general, decrease with increasing current, but since this resistance is but a small fraction of the resistance of rectifier R in the high resistance direction, this decrease will not play a significant part inoffsetting the increase in the resistance of rectifier R Since the resistance of resistor F will remain substantially constant for current changes which are not excessive, the drop across resistor F will increase but slightly, the greater portion of the increase of voltage at the source being absorbed in rectifier R with the result that the percentage increase in the voltage across load L will be much smaller than the corresponding increase at the source.

Rectifier R is similar in all respects to rectifier R except that it is poled in the reverse direction, so that when the instantaneous polarity of current at the source becomes reversed, the functions of rectifiers R and R become interchanged, with the result that the regulating effect of the apparatus is maintained for both directions of current flow. For sensitive regulation, the drop across the resistance of each rectifier R and R in the high resistance direction should be made of the same order as'the drop across resistor F. To accomplish this result, instead of using a single disc rectifier as illustrated for simplicity, a number of discs may be arranged in series or in parallel, or any suitable combination of the twoas may be required by the voltage of the source, impedance of load L, or degree of regulation desired. a

It will be apparent from the above that should the voltage at the source decrease, the

- resistance of rectifiers R and R inthe'high resistance direction will decrease,causing the drop across theserectifierstodeoreasebyaper-' Y.

' drop across resistor 'and'load the same" as before the change, so that the decrease'in' centage greater than the percentage decrease in current, tending thereby'to maintain the voltage at the source will be'reflected in a smaller degree at the load. Should it be desired for any'reason to accentuate theload voltage changes resulting from changes in the source voltage, this result can be accomplished by connecting the load across terminals G D, as illustrated by load M in the drawing. Although I have shown a load connected across each pair of terminals C-D and DE, in general, one load only will be used, the choice depending upon whether it is desired to decrease or to accentuate the source voltage changes. However, both types of-regulation may be obtained simultaneously, if desired.

In order to increase the sensitivity of the regulating apparatus illustrated in Fig. 1, I have provided the arrangement shown in Fig. 2, in which I take advantage of both characteristics of the copper oxide rectifier,

- as mentioned hereinbefore, namely, a decrease in the rectifier resistance in the low resistance direction with an increase in current density, as well as an increase in. the rectifier resistance in the high resistance direction with an increase in curent density. The rectifiers R and R are similar to the rectifiers R and R of Fig; 1, but resistor F is replaced by oppositely poled rectifiers or rectifier groups R and R connected in parallel.

R functions in a similar manner to rectifier R of Fig. 1, and is so proportioned that an increase'in resistance in the high resistance direction is produced therein when the current density is increased. Rectifiers R and R are identical with rectifiers R and R", respectively, except that theyare poled in the opposite direction.

It will be apparent from the foregoing, that when the voltage acrossthe source A'B becomes increased, the drop across the-portion of the circuit involving rectifiers R and R will decrease, and the drop across the portion of the circuit involving rectifiers R and R will increase, from: the values which these respective drops would have, if ordinary resistors had been used in place of'the' rectifiers.

Therefore, a smaller increase in load; voltage across terminals C'D will result for a given increase source .voltage than is possible with the'arrangementof F ig'. 1, due to the added stabilizing influence of rectifiers R and R, which is not supplied by resistor F. To accentuate source voltage variations, ,the load would be connected across terminals D-E,in'stead of across terminals C -D.

.The arrangement illustrated in Fig. 3 is similar to that of Fig. 2 except that, it, is

suitable for use with unidirectional currents only. As will be seen from the figure, i ectifiers R and R which are efi'ective in pro viding regulation for current flowing in the reverse direction in Fig 2, have been omitted. The principle of operation of the apparatus shown in Fig, 3 is the same as that already described in connection with Fig. 2.

One advantage of the arrangcmentsillustrated in Figs. 2 and 3 over that shown in Fig. 1 is that the former arrangements eX- hibita tendency toward compensation for changes. in ambient temperature. That is, considering Fig. 3 for example, if the temperature ofthe air surrounding rectifiers R and B should increase, the resistance of both rectifiers will decrease, so that the resistance ratio of rectifier R to R will tend to remain constant within reasonable temperature limits. A similar effect could be obtained with the apparatus of Fig. 1 if the resistor F were made of material having a negative temperature coeflicient of resistance of the order of the temperature coeificient of resistance of the copper oxide rectifiers being used.

Although I have herein shown and described only three forms of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination, a source of alternating current of variable voltage, a resistor having one terminal connected with a terminal of said source, two oppositely poled copper oxide rectifiers connected in series from the other terminal of sald reslstor to the remaining termlnal of sald source, and a load connected across said two rectifiers.

resistance in accordance 3. In combination, a source of alternating current of variable voltage, a regulating cir-- cuit comprising an impedance having one terminal connected with a terminal of said source and two oppositely poled copper oxide rectifiers connected in series from the other terminal of said impedance to the remaining terminal of said source, and a load connected across a portion of said regulating circuit.

4. In combination, a source of direct current of variable voltage, two oppositely poled copper oxide rectifiers connected in series across said source, and a load connected across one of said rectifiers.

5. In combination, a source of alternating current of variable voltage; a first and a second rectifier group connected in series across said source, said first group comprising two oppositely poled copper oxide rectifiers connected in multiple and said second grou comprising two oppositely poled copper oxi e rectifiers connected in series; and a load connected across one of said rectifier groups.

6. In combination, asource of alternating current of variable voltage; a regulating circuit comprising a resistor having a negative temperature coefficient and having one terminal connected with a terminal of said source, and two oppositely poled copper oxide rectifiers connected in series from the other terminal of said resistor to the remaining terminal of said source; and a load connected across a portion of said regulating circuit.

7. In combination, a source of alternating current of variable voltage; a regulating circuit comprising an impedance havin one terminal connected with a terminal 0 said source, and two oppositely poled asymmetric units connected in series from the other terminal of said impedance to the remaining terminal of said source, each of said asymmetric units having the characteristic of varying its "th variations in the current density therein when the current flow through said unit is in the direction wherein the higher resistancewf the unit is encountered; and a load connected across a portion of said regulating circuit.

In testimony whereof I aflix my signature.

\ \LEE DEVOL. 

